An accurate determination of a spacecraft’s radio frequency electromagnetic field environment during launch and flight is critical for mission success. Typical fairing structures consist of a parabolic nose and a cylindrical core with diameters of 1 to 5 meters resulting in electrically large dimensions for typical operational sources at S, C and X band where the free space wavelength varies from 0.15 m to 0.03 m. These electrically large size and complex structures at present have internal fairing electromagnetic field evaluation that is limited to general approximation methods and some test data. Though many of today’s computational electromagnetic tools can model increasingly complex and large structures, they still have many limitations when used for field determination in electrically large cavities. In this dissertation, a series of test anchored, full wave computational electromagnetic models along with a novel application of the equivalent material property technique are presented to address the electrical, geometrical, and boundary constraints for electromagnetic field determination in composite fairing cavity structures and fairings with acoustic blanketing layers. Both external and internal excitations for these fairing configurations are examined for continuous wave and transient sources. A novel modification of the Nicholson Ross Weir technique is successfully applied to both blanketed aluminum and composite fairing structures and a significant improvement in computational efficiency over the multilayered model approach is obtained. The advantages and disadvantages of using commercially available tools by incorporating Multilevel Fast Multipole Method (MLFMM) and higher order method of moments (HO MoM) to extend their application of MoM to electrically large objects is examined for each continuous wave transmission case. The results obtained with these models are ii compared with those obtained using approximation techniques based on the Q factor, commonly utilized in the industry, and a significant improvement is seen in a prediction of the fields in these large cavity structures. A statistical distribution of data points within the fairing cavity is examined to study the nature of the fairing cavity field distribution and the effect of the presence of a spacecraft load on these fields is also discussed. In addition, a model with external application of Green’s function is examined to address the shielding effectiveness of honeycomb panels in a fairing cavity. Accurate data for lightning induced effects within a fairing structure is not available and hence in this dissertation, a transmission line matrix method model is used to examine induced lightning effects inside a graphite composite fairing structure. The simulated results are compared with test data and show good agreement.

One of the major challenges in cancer treatment is delivering high enough doses of active substance specifically to cancer cells without accumulation in healthy organs. Pretargeting has emerged as a potential solution, where the delivery of a cancer recognizing (primary) agent and a cancer killing (secondary) agent are separated. Pretargeted cancer therapy utilizing PNA probes has proved to be a promising approach to selectively deliver toxic payloads to cancer cells while minimizing accumulation in healthy organs. The aim of this project was to develop a new set of secondary PNA probes specifically designed for PNA pretargeted delivery of cytotoxic drugs. A HER2-specific Affibody molecule, ZHER2:2891-SR-H6, was recombinantly produced in E. coli before being conjugated to a primary PNA hybridization probe, HP9, through sortase A-mediated ligation, to produce the primary agent, ZHER2:2891-SR-HP9. Circular dichroism (CD) spectroscopy confirmed the stability of the constructs with high melting temperatures of 71.2 and 73.7 °C. Surface plasmon resonance (SPR) analysis demonstrated high binding affinity to HER2, slightly affected by PNA conjugation. Three new secondary PNA hybridization probes were designed, differing mainly in prevalence and position of a hydrophilic PEG molecule. The probes were produced by solid phase peptide synthesis and conjugated to the cytotoxic drug DM1 through maleimide-cysteine coupling. Analytical RP-HPLC evaluation revealed a slightly higher apparent hydrophobicity for the probe with PEG in the main chain. All three secondary probes displayed high affinity to the primary probe with KD values between 498–505 pM. In vitro cytotoxicity studies on HER2-overexpressing cells demonstrated comparable potent cytotoxic activity for pre-incubated primary and secondary probes with IC50 values of 10–14 nM. These results indicate the successful development of three PNA-drug conjugates for pretargeted delivery of cytotoxic drugs.

A new passive treatment to reduce sound transmission into payload fairing at low frequency is investigated. This new solution is composed of optimally damped vibration absorbers (DVA) and optimally damped Helmholtz resonators (HR). A fully coupled structural-acoustic model of a composite cylinder excited by an external plane wave is developed as a first approximation of the system. A modal expansion method is used to describe the behavior of the cylindrical shell and the acoustic cavity; the noise reduction devices are modeled as surface impedances. All the elements are then fully coupled using an impedance matching method. This model is then refined using the digitized mode shapes and natural frequencies obtained from a fairing finite element model. For both models, the noise transmission mechanisms are highlighted and the noise reduction mechanisms are explained. Procedures to design the structural and acoustic absorbers based on single degree of freedom system are modified for the multi-mode framework. The optimization of the overall treatment parameters namely location, tuning frequency, and damping of each device is also investigated using genetic algorithm. Noise reduction of up to 9dB from 50Hz to 160Hz using 4% of the cylinder mass for the DVA and 5% of the cavity volume for the HR can be achieved. The robustness of the treatment performance to changes in the excitation, system and devices characteristics is also addressed. The model is validated by experiments done outdoors on a 10-foot long, 8-foot diameter composite cylinder. The excitation level reached 136dB at the cylinder surface comparable to real launch acoustic environment. With HRs representing 2% of the cylinder volume, the noise transmission from 50Hz to160Hz is reduced by 3dB and the addition of DVAs representing 6.5% of the cylinder mass enhances this performance to 4.3dB. Using the fairing model, a HR+DVA treatment is designed under flight constraints and is implemented in a real Boeing fairing. The treatment is composed of 220 HRs and 60 DVAs representing 1.1% and 2.5% of the fairing volume and mass respectively. Noise reduction of 3.2dB from 30Hz to 90Hz is obtained experimentally. As a natural extension, a new type of adaptive Helmholtz resonator is developed. A tuning law commonly used to track single frequency disturbance is newly applied to track modes driven by broadband excitation. This tuning law only requires information local to the resonator simplifying greatly its implementation in a fairing where it can adapt to shifts in acoustic natural frequencies caused by varying payload fills. A time domain model of adaptive resonators coupled to a cylinder is developed. Simulations demonstrate that multiple adaptive HRs lead to broadband noise reductions similar to the ones obtained with genetic optimization. Experiments conducted on the cylinder confirmed the ability of adaptive HRs to converge to a near optimal solution in a frequency band including multiple resonances. / Ph. D.

Nowadays, numerous applications of active sound transmission control require lightweight partitions with high transmission loss over a broad frequency range and simple control strategies. In this work an active-passive sound transmission control approach is investigated that potentially addresses these requirements. The approach involves the use of lightweight stiff panels, or tiles, attached to a radiating base structure through active-passive soft mounts and covering the structure surface. The resulting double-partition configuration was shown to have good high frequency passive isolation, but poor low frequency transmission loss due to the coupling of the tiles to the base vibration through the air gap. The low frequency transmission loss performance of the partition was increased by using the active mounts to cancel the local volume velocity of the tiles. The use of a decentralized control approach with independent single channel controllers for each tile facilitates the implementation of a multiple tile system in a large scale application. A coupled structural-acoustic model based on an impedance mobility matrix approach was formulated to investigate the potential performance of active-passive tile approach in controlling sound transmission through plates. The model was initially applied to investigate the sound transmission characteristics of a double-panel partition consisting of a single tile-plate configuration and then extended to model a partition consisting of multiple-tiles mounted on a plate. The system was shown to have significant passive performance above the mass-spring-mass resonance of the double-panel system. Both feedback and feedforward control approaches were simulated and shown to significantly increase the transmission loss of the partition by applying control forces in parallel with the mounts to reduce the tile normal velocity. A correspondent reduction in sound radiated power was obtained over a broad frequency range limited by the tile stiffness. The experimental implementation of the active-passive tile approach for the control of sound transmission through plates was also performed. Two main experimental setups were utilized in the investigations, the first consisting of a single tile mounted on a clamped plate and the other consisting of four active tiles mounted of a simply supported plate. Tile prototypes were implemented with lightweight stiff panels and integrated active-passive mounts were implemented with piezoelectric Thunder actuators. Both analog feedback and digital feedforward control schemes where designed and implemented with the objective of reducing the normal velocity of the tiles. Experimental results have demonstrated significant broad frequency range reductions in the sound transmission through the partition by active attenuation of the tile velocity. In addition, the experiments have shown that decentralized control can be successfully implemented for multiple tiles systems. The active-passive sound transmission control characteristics of the systems experimentally studied were observed to be in accordance with the analytical results. / Ph. D.

The research presented in this thesis focuses on the use of feedback control for lowering acoustic levels within launch vehicle payload fairings. Due to the predominance of conical geometries within payload fairings, our work focused on the analytical modeling of conical shrouds using modal and impedance based models. Incorporating an actuating boundary condition within a sealed enclosure, resonant frequencies and mode shapes were developed as functions of geometric and mechanical parameters of the enclosure and the actuator. Using a set of modal approximations, a set of matrix equations have been developed describing the homogeneous form of the wave equation. Extending to impedance techniques, the resonant frequencies of the structure were again calculated, providing analytical validation of each model. Expanding this impedance model to first order form, the acoustic model has been coupled with actuator dynamics yielding a complete model of the system relating pressure to control voltage. Using this coupled state-space model, control design using Linear Quadratic Regulator and Positive Position Feedback techniques has also been presented. Using the properties of LQR analysis, an analytical study into the degree of coupling between actuator and cavity as a function of actuator resonance has been conducted. Constructing an experimetnal test-bed for model validation and control implementation, a small sealed enclosure was built and outfitted with sensors. Placing a control speaker at the small end of the cone the large opening was sealed with a rigid termination. An internal acoustic source was used to excite the system and pressure measurements were captured using an array of microphones located throughout the conic section. Using the parameters of this experimental test-bed, comparisons were made between LQR and PPF control designs. Using an impulse disturbance to excite the system, LQR simulations predicted reductions of 53.2% below those of the PPF design, while the control voltages corresponding to these reductions were 43.8% higher for LQR control. Actual application of these control designs showed that the ability to manually set PPF gains made this design technique much more convenient for actual implementation. Yielding overall attenuation of 38% with control voltages below 200 mV, single-channel low authority control was seen to be an effective solution for low frequency noise reduction. Control was then expanded to a larger geometry representative of Minotaur fairings. Designing strictly from experimental results, overall reductions of 38.5% were observed. Requiring slightly larger control voltages than those of the conical cavity, peak voltages were still found to be less than 306 mV. Extrapolating to higher excitation levels of 140 dB, overall power requirements for 38.5% pressure reductions were estimated to be less than 16 W. / Master of Science

This thesis focuses on adaptive feedback control for low frequency acoustic energy absorption in acoustic enclosures. The specific application chosen for this work is the reduction of high interior sound pressure levels (SPL) experienced during launch within launch vehicle payload fairings. Two acoustic enclosures are used in the research: the first being a symmetric cylindrical duct and the other being a full scale model of a payload fairing. The symmetric cylindrical duct is used to validate the ability of the adaptive controller to compensate for large changes in the interior acoustical properties. The payload fairing is used to validate that feedback control, for a large geometry, does absorb acoustic energy. The feedback controller studied in this work is positive position feedback (PPF) used in conjunction with high and low pass Butterworth filters. An algorithm is formed from control experiments for setting the filter parameters of the PPF and Butterworth filters from non-adaptive control simulations and tests of the duct and payload fairing. This non-adaptive control shows internal SPL reductions of 2.2 dB in the cylindrical duct for the frequency range from 100 to 500 Hz and internal SPL reductions of 4.2 dB in the full scale fairing model for the frequency range from 50 to 250 Hz. The experimentally formed control algorithm is then used as the basis for an adaptive controller that uses the collocated feedback signal to actively tune the control parameters. The cylindrical duct enclosure with a movable end cap is used to test the adaptation properties of the controller. The movable end cap allows the frequencies of the acoustic modes to vary by more than 20 percent. Experiments show that a 10 percent change in the frequencies of the acoustic modes cause the closed-loop system to go unstable with a non-adaptive controller. The closed-loop system with the adaptive controller maintains stability and reduces the SPL throughout the 20 percent change of the acoustic modes' frequencies with a 2.3 dB SPL reduction before change and a 1.7 dB SPL reduction after the 20 percent change. / Master of Science

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The accuracy of channel estimation plays a crucial role in the demodulation of data symbols sent across an unknown wireless medium. In this work a new analytical expression for the channel estimation error of a multiple input multiple output (MIMO) system is obtained when the wireless medium is continuously changing in the temporal domain. Numerical examples are provided to illustrate our findings.

International Telemetering Conference Proceedings / October 26-29, 1987 / Town and Country Hotel, San Diego, California / Engineering requirements and design characteristics of the coherent throughput relay system which supports East Coast pre-launch checkout of NASA's Space Shuttle and its Payloads are presented. The Relay system is required to provide communications through NASA's Tracking and Data Relay Satellite System for the Shuttle and Payload-Users while they are encapsulated in the launch preparation facilities at the John F. Kennedy Space Center and the Eastern Test Range, Florida. The Relay system is required to be transparent to its users' data at all rates up to three MB/s at S-band and 300 MB/s at Ku-band. Noise and group-delay distortion are major contributors to wide band RF signal degradation. These were major factors in the Relay system design. Antenna design, pointing angle and location were constrained by the need to maximize end-to-end RF signal isolation at both S-band and KU-band, simultaneous forward and return frequencies. System characteristics and link analysis are also presented. In addition, a similar Data Relay located at Vandenberg Air Force Base is briefly described.

Autonomous aerial transportation has multiple potential applications including emergency cases and rescue missions where ground intervention may be difficult. In this context, the following work will address the control of multi-agent Vertical Take-off and Landing aircraft (VTOL) transportation system. We develop a decentralized method. The advantage of such a solution is that it can provide better maneuverability and lifting capabilities compared to existing systems. First, we consider a cooperative group of VTOLs transporting one payload. The main idea is that each agent perceive the interaction with other agents as a disturbance while assuming a negotiated motion model and imposing certain magnitude bounds on each agent. The theoretical model will be then validated using a numerical simulation illustrating the interesting features of the presented control method. Results show that under specified disturbances, the algorithm is able to guarantee the tracking with a minimal error. We describe a toolbox that has been developed for this purpose. Then, a system of multiple VTOLs lifting payloads will be studied. The algorithm assures that the VTOLs are coordinated with minimal communication. Additionally, a novel gripper design for ferrous objects is presented that enables the transportation of ferrous objects without a cable. Finally, we discuss potential connections to human in the loop transportation systems.

Many potentially useful applications that broadly fall under the umbrella of payload transportation operations have been proposed for aerial towed-cable (ATC) systems, namely the precise capture and delivery of payloads. There remain outstanding issues concerning the dynamics and control of ATC systems that are inhibiting the near-term demonstration of these applications. The development of simplified representations of ATC systems that retain the important dynamics, yet are simple enough for use in control system development is limited. Likewise, little research exists into the development of controllers for ATC systems, especially the development of towing strategies and cable-based control techniques for rendezvous and payload transportation. Thus, this thesis presents novel research into the development of control strategies and simulation facilities that redress these two major anomalies, thereby overcoming a number of hitherto unresolved issues. The primary objective of this thesis is to develop innovative non-linear optimal control systems to manoeuvre a cable towed beneath an aircraft to transport payloads both to and from surface locations. To appropriately satisfy this objective, accurate and efficient modelling capabilities are proposed, yielding the equations of motion for numerous models of the ATC system. A series of techniques for improving the representativeness of simple dynamical models were developed. The benefits of using these procedures were shown to be significant and possible without undue complexity or computational expense. Use of such techniques result in accurate simulations and allow representative control systems to be designed. A series of single and multi-phase non-linear optimal control problems for ATC systems are then formally proposed, which were converted into non-linear programming problems using direct transcription for expedient solution. The possibility of achieving accurate, numerous instantaneous rendezvous of the cable tip with desired surface locations on the ground, in two and three-dimensions, is successfully demonstrated. This was achieved through the use of deployment and retrieval control of the cable and/or aircraft manoeuvring. The capability of the system to safely and accurately transport payloads to and from the surface via control of the cable and/or aircraft manoeuvring is also established. A series of parametric studies were conducted to establish the impact that various parameters have on the ability of the system to perform various rendezvous and payload transportation operations. This allowed important insights into to the nature of the system to be examined. In order for the system to perform rendezvous and payload transportation operations in the presence of wind gusts, a number of simple closed loop optimal feedback controllers were developed. These feedback controllers are based on the linear quadratic regulator control methodology. A preliminary indication of the robustness of ATC systems to wind gusts is provided for through a succession of parametric investigations. The performance of the closed-loop system demonstrates that precise and robust control of the ATC system can be achieved for a wide variety of operating conditions. The research presented in this thesis will provide a solid foundation for further advancing the development of aerial tether payload transportation technology.